The present invention relates to the field of communications in general, and more particularly, to call configuration in satellite radiotelephone systems.
Satellite radiotelephone communications systems are widely used to provide radiotelephone communications among satellite radiotelephones and with cellular and conventional wired telephones. For example, the satellite radiotelephone system 101 shown in FIG. 1 may allow a first satellite radiotelephone 100 to communicate with a second satellite radiotelephone 105 via a satellite 110. The first and second satellite radiotelephones 100, 105 can conduct a call by transmitting signals from the transmitting satellite radiotelephone to the satellite 110 that relays the signals to a switching center 115 which relays the signals to the receiving satellite radiotelephone via the satellite 110 over first, second, and third channels 120a-c (i.e., a dual hop call). Unfortunately, the dual hop call configuration described above may introduce long delays in signal transmission due to the distance between the first and second satellite radiotelephones 100, 105 and the satellite 110.
Therefore calls in satellite radiotelephone systems 101 between the first and second satellite radiotelephones 100, 105 may be routinely conducted as single hop calls. In particular, the switching center 115 may determine that the first and second satellite radiotelephones 100, 105 are both satellite radiotelephones served via the satellite 110. The call from the first satellite radiotelephone 100 to the second satellite radiotelephone 105 may then be conducted over a transmission path 125 via the satellite 110 (i.e., a single hop). In other words, the single hop configuration may reduce delays in signal transmission by eliminating transmissions between the switching center 115 and the satellite 110 once the call is in an active state. For example, once the second satellite radiotelephone 105 accepts the call, the signals transmitted between the first and second satellite radiotelephones are not routed through the switching center 115.
Unfortunately, the configuration of such single hop calls may introduce some disadvantages. For example, it may be difficult to encode voice data transmitted between the first and second satellite radiotelephones 100, 105 in a single hop configuration. Such encoding is typically performed by systems accessible to the switching center 115 rather than the satellite 110. Consequently, the elimination of signaling between the satellite 110 and the switching center 115 in the single hop call may reduce the accessibility of the encoding systems. In addition, call services, such as call conferencing between three or more parties, is typically performed by systems accessible to the switching center 115. Accordingly, a single hop call configuration may also reduce the availability of those services to the first and second satellite radiotelephones 100, 105 involved in the single hop call.
It is, therefore, an object of the present invention to provide satellite radiotelephones, systems and methods of operating satellite radiotelephone systems which may provide improved performance in how calls are conducted in satellite radiotelephone systems.
These, and other objects of the present invention, may be provided by methods, user terminals, and systems that conduct calls from a satellite user terminal to a user terminal via a satellite in a satellite radiotelephone system by transmitting information from the satellite user terminal to the satellite radiotelephone system via the satellite. The information includes a request to conduct an active state of the call from the satellite user terminal to the user terminal via a ground segment in the satellite radiotelephone system. The active state of the call is conducted from the satellite user terminal to the user terminal via the ground segment based on the request. In other words, single hop routing of a dual-hop call may be selectively bypassed at the request of a mobile terminal.
In one embodiment of the present invention, the call is conducted as a single or dual hop call under the control of the satellite radiotelephone that initiates the call. In particular, a first satellite radiotelephone calling a second satellite radiotelephone can instruct satellite radiotelephone system to conduct the call as a dual hop call by transmitting a suspension code to a switching center, thereby possibly avoiding a default action by the switching center to configure the call as a single hop. Consequently, data transmitted between the first and second satellite user terminals may be processed by systems available to the ground segment. For example, audio data may be encoded or other users may join the call between the first and second satellite radiotelephones using a teleconference function available to the ground segment.
In a further aspect of the present invention, a determination is made whether the user terminal being called is a second satellite user terminal that communicates with the satellite radiotelephone system via the satellite. The active state of the call is conducted between the satellite user terminal and the user terminal via the ground segment in response to the request if the user terminal is a second satellite user terminal that communicates with the satellite radiotelephone system via the satellite.
In another aspect of the present invention, the information includes a suspension code or suspension message which requests the suspension of single hop call configuration for the active state of the call. The suspension code can comprise a suffix or prefix associated with a telephone number that identifies the second satellite user terminal in the satellite radiotelephone system.